Roller cone drill bits with enhanced cutting elements and cutting structures
Roller cone drill bits are provided with cutting elements and cutting structures optimized for efficient drilling of soft and medium formations interspersed with hard stringers. The cutting elements and cutting structures may be satisfactorily used to drill downhole formations with varying amounts of hardness. The cutting elements and cutting structures may also be optimized to reduce tracking and increase wear resistance.
Latest Halliburton Energy Services, Inc. Patents:
- Method of calculating viscous performance of a pump from its water performance characteristics and new dimensionless parameter for controlling and monitoring viscosity, flow and pressure
- Ranging solenoid coil transmitter around downhole bottom hole assembly elements
- Interactive virtual reality manipulation of downhole data
- Continuous extruded solids discharge
- Geopolymer formulations for mitigating losses
This continuation-in-part application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/549,354 entitled “Roller Cone Drill Bits with Enhanced Cutting Elements and Cutting Structures” filed Mar. 2, 2004.
This application is a continuation-in-part application of U.S. Continuation patent application Ser. No. 10/189,305 entitled “Roller-Cone Bits, Systems, Drilling Methods, and Design Methods with Optimization of Tooth Orientation” filed on Jul. 2, 2002, now abandoned, which is a continuation application of U.S. Continuation patent application Ser. No. 09/629,344 entitled “Roller-Cone Bits, Systems, Drilling Methods and Design Methods with Optimization of Tooth Orientation” filed Aug. 1, 2000, now U.S. Pat. No. 6,412,577, which is a continuation of U.S. patent application Ser. No. 09/387,304 entitled “Roller-Cone Bits, Systems, Drilling Methods, and Design Methods with Optimization of Tooth Orientation” filed Aug. 31, 1999, now U.S. Pat. No. 6,095,262, which claims priority from U.S. Provisional Application No. 60/098,442 filed Aug. 31, 1998.
This application is copending to U.S. Continuation patent application Ser. No. 10/756,109 entitled “Roller-Cone Bits, Systems, Drilling Methods, and Design Methods with Optimization of Tooth Orientation” filed Jan. 13, 2004.
This application is also to continuation application of U.S. patent application Ser. No. 10/766,494 entitled “Roller-Cone Bits, Systems, Drilling Methods, and Design Methods with Optimization of Tooth Orientation” filed Jan. 28, 2004, now abandoned.
TECHNICAL FIELDThe present invention is related to roller cone drill bits used to form wellbores in subterranean formations and more particularly to arrangement and design of cutting elements and cutting structures for optimum performance of an associated drill bit.
BACKGROUND OF THE INVENTIONA wide variety of roller cone drill bits have previously been used to form wellbores in downhole formations. Such drill bits may also be referred to as “rotary” cone drill bits. Roller cone drill bits frequently include a bit body with three support arms extending therefrom. A respective cone is generally rotatably mounted on each support arm opposite from the bit body. Such drill bits may also be referred to as “tricone drill bits” or “rock bits”.
A wide variety of roller cone drill bits have been satisfactorily used to form wellbores. Examples include roller cone drill bits with only one support arm and one cone, two support arms with a respective cone rotatably mounted on each arm and four or more cones rotatably mounted on an associated bit body. Various types of cutting elements and cutting structures such as compacts, inserts, milled teeth and welded compacts have also been used in association with roller cone drill bits.
Cutting elements and cutting structures associated with roller cone drill bits typically form a wellbore in a subterranean formation by a combination of shearing and crushing adjacent portions of the formation. The shearing motion may also be described as each cutting element scraping portions of the formation during rotation of an associated cone. The crushing motion may also be described as each cutting element penetrating portions of the formation during rotation of an associated cone. Within the well drilling industry it is generally accepted that shearing or scraping motion of a cutting element is a more efficient technique for removing a given volume of formation material from a wellbore as compared with a cutting element crushing or penetrating the same formation. Fixed cutter drill bits, sometimes referred to as drag bits or PDC drill bits, typically have cutting elements or cutting structures which only shear or scrape during contact with a formation. Therefore, fixed cutter drill bits are often used to form a wellbore in soft and medium formations. Conventional roller cone drill bits often require more time to drill soft and medium formations as compared to fixed cutter drill bits.
The magnitude of the shearing motion or scraping motion associated with cutting structures of roller cone drill bits depends upon various factors such as the offset of each cone and associated cone profile. The magnitude of the crushing motion or penetrating motion associated with cutting structures of roller cone drill bits depends upon various factors such as weight on the bit, speed of rotation and geometric configuration of associated cutting structures and associated cone profiles. Roller cone drill bits designed for drilling relatively soft formations often have a larger cone offset value as compared with roller cone drill bits designed for drilling hard formations. Roller cone drill bits having cutting structures formed by milling rows of teeth on each cone are often used for drilling soft formations. Roller cone drill bits having cutting elements and cutting structures formed from a plurality of hard metal inserts or compacts are often used for drilling medium and hard formations. It is well known in the roller cone drill bit industry that drilling performance may be improved by orientation of cutting elements and cutting structures disposed on associated cones. Roller cone drill bits often remove a greater volume of formation material by shearing or scraping as compared with crushing or penetrating of the same formation.
SUMMARY OF THE DISCLOSUREIn accordance with teachings of the present disclosure, a roller cone drill bit may be formed with at least one cone having at least one row of cutting elements oriented such that the crest of one element extends generally perpendicular to an associated scraping direction and the crest of an adjacent cutting element extends generally parallel with the associated scraping direction. The remaining cutting elements in the one row are preferably arranged with alternating crests extending generally perpendicular to the associated scraping direction and parallel with the associated scraping direction.
Another aspect of the present invention includes providing a roller cone drill bit having at least one cone with at least one row of cutting elements oriented such that the crest of each cutting element is arranged generally perpendicular to an associated scraping direction. An adjacent row of cutting elements on the same cone may be oriented so that the crest of each cutting element extends generally parallel with the associated scraping direction.
A further embodiment of the present invention includes forming a roller cone drill bit having a gauge row formed on a first cone with the crest of each cutting element aligned generally perpendicular to an associated scraping direction to optimize volume of material removed from a formation by the gauge row. A gauge row may be formed on a second cone with the crest of each cutting element aligned generally parallel with an associated scraping direction to optimize penetration of the formation by the gauge row. A gauge row may be formed on a third cone with an alternating arrangement of cutting elements defined in part by the crest of one cutting element disposed generally perpendicular to the associated scraping direction and the crest of an adjacent cutting element disposed generally parallel with the associated scraping direction.
For some applications roller cone drill bits may be formed in accordance with teachings of the present invention with each cone having a plurality of cutting elements with different shapes, sizes and/or orientations. Also, one or more cutting elements may be formed from two or more different types of material.
Technical benefits of the present invention include forming roller cone drill bits which may be efficiently used to drill mixed formations of soft and hard materials. A roller cone drill bit formed in accordance with teachings of the present invention may include cutting structures which provide optimum scraping motion to remove relatively large volumes of material from soft formations. Portions of the cutting structures may extend generally parallel with the scraping motion to improve penetration or crushing of hard materials dispersed in the formation. Another aspect of the present invention includes forming cutting elements and cutting structures on a cone to produce void spaces or craters in the bottom of a wellbore to enhance fracturing and splitting of formation materials adjacent to the void spaces or craters. Cutting elements and cutting structures formed in accordance with teachings of the present invention may be used to reduce and/or eliminate tracking and vibration of associated cones.
Technical benefits of the present invention include providing roller cone drill bits with cutting elements and cutting structures operable to efficiently drill a wellbore in soft and medium formations with multiple hard stringers dispersed within both types of formations. Forming a roller cone drill bit with cutting elements and cutting structures incorporating teachings of the present invention may substantially reduce wear of associated cutting elements and cutting structures and increase downhole drilling life of the drill bit.
A more complete and thorough understanding of the present embodiments and advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings, in which like reference numbers indicate like features, and wherein:
Preferred embodiments of the invention and its advantages are best understood by reference to
The terms “cutting element” and “cutting elements” may be used in this application to include various types of compacts, inserts, milled teeth and welded compacts satisfactory for use with roller cone drill bits. The terms “cutting structure” and “cutting structures” may be used in this application to include various combinations and arrangements of cutting elements formed on or attached to one or more cone assemblies of a roller cone drill bit.
The terms “crest” and “longitudinal crest” may be used in this application to describe portions of a cutting element or cutting structure that makes initial contact with a downhole formation during drilling of a wellbore. The crest of a cutting element will typically engage and disengage the bottom of a wellbore during rotation of a roller cone drill bit and associated cone assemblies. The geometric configuration and dimensions of a crest may vary substantially depending upon specific design and dimensions of an associated cutting element or cutting structure.
As discussed later in more detail cutting elements and cutting structures formed in accordance with teachings of the present invention may have various designs and configurations. Cutting elements formed in accordance with teachings of the present invention will preferably include at least one crest.
A drill string (not expressly shown) may be attached to threaded portion 22 of drill bit 20 or drill bit 320 to both rotate and apply weight or force on associated cone assemblies 30 and 330. Cutting or drilling action associated with drill bits 20 and 320 occurs as cone assemblies 30 and 330 roll around the bottom of a wellbore. The inside diameter of the resulting wellbore corresponds approximately with the combined outside diameter or gauge diameter associated with cone assemblies 30 and 330. For some applications various types of downhole motors (not expressly shown) may also be used to rotate a roller cone drill bit incorporating teachings of the present invention. The present invention is not limited to roller cone drill bits associated with conventional drill strings.
For purposes of describing various features of the present invention cone assemblies 30 may be identified as 30a, 30b and 30c. Cone assemblies 330 may be identified as 330a, 330b and 330c. Cone assemblies 30 and 330 may sometimes be referred to as “rotary cone cutters”, “roller cone cutters” or “cutter cone assemblies”.
Roller cone drill bits 20 and 320 may be used to form a wellbore (not expressly shown) in a subterranean formation (not expressly shown) by cone assemblies 30 and 330 rolling around the bottom of the wellbore in response to rotation of an attached drill string. Roller cone drill bits 20 and 320 typically form boreholes by crushing or penetrating formation materials at the bottom of a borehole and scraping or shearing formation materials from the bottom of the borehole using cutting elements 60 and 360.
Roller cone drill bit 20 preferably includes bit body 24 having tapered, externally threaded portion 22 adapted to be secured to one end of a drill string. Bit body 24 preferably includes a passageway (not expressly shown) to communicate drilling mud or other fluids from the well surface through the drill string to attached drill bit 20. Drilling mud and other fluids may exit from nozzles 26. Formation cuttings and other debris may be carried from the bottom of a borehole by drilling fluid ejected from nozzles 26. The drilling fluid generally flows radially outward between the underside of roller cone drill bit 20 and the bottom of an associated borehole. The drilling fluid may then flow generally upward to the well surface through an annulus (not expressly shown) defined in part by the exterior of drill bit 20 and associated drill string and the inside diameter of the wellbore.
For embodiments of the present invention as represented by drill bit 20, bit body 24 may have three (3) substantially identical support arms 32 extending therefrom. The lower portion of each support arm 32 opposite from bit body 24 preferably includes respective shaft or spindle 34. Spindle 34 may also be referred to as a “bearing pin”. Each cone assembly 30a, 30b and 30c preferably includes respective cavity 48 extending from backface 42. The dimensions and configuration of each cavity 48 are preferably selected to receive associated spindle 34. Portions of cavity 48 are shown in
Cone assemblies 30a, 30b and 30c may be rotably attached to respective spindles 34 extending from support arms 32. Each cone assembly 30a, 30b and 30c includes a respective axis of rotation 36 (sometimes referred to as “cone rotational axis”) extending at an angle corresponding with the relationship between spindle 34 and associated support arm 32. Axis of rotation 36 often corresponds with the longitudinal center line of associated spindle 34.
For embodiments shown in
Compacts 40 and cutting elements 60 may be formed from a wide variety of hard materials such as tungsten carbide. The term “tungsten carbide” includes monotungsten carbide (WC), ditungsten carbide (W2C), macrocrystalline tungsten carbide and cemented or sintered tungsten carbide. Examples of hard materials which may be satisfactorily used to form compacts 40 and cutting elements 60 include various metal alloys and cermets such as metal borides, metal carbides, metal oxides and metal nitrides. An important feature of the present invention includes the ability to select the type of hard material which provides desired abrasion, wear and erosion resistance in a cost effective, reliable manner and provides optimum downhole drilling performance.
Bearing 50 supports radial loads associated with rotation of cone assembly 30a relative to spindle 34. Thrust bearings 54 support axial loads associated with rotation of cone assembly 30a relative to spindle 34. Bearings 52 may be used to securely engage cone assembly 30a with spindle 34.
For embodiments shown in
Based on various factors such as dimensions of drill bit 20, offset angle of each cone assembly 30a, 30b and 30c, specific location of each cutting element 60 on cone assemblies 30a, 30b and 30c, movement of each cutting element 60 along a respective path or track will vary relative to rotational axis 38 of drill bit 20. Curved path 70a as shown in
Each cone assembly 30a, 30b and 30c and associated cutting elements 60 will have a respective orientation and scraping direction associated with optimum removal of material from a downhole formation and a respective orientation for optimum crushing or penetration of the downhole formation relative to the scraping direction. Arrows 70 will be used throughout this application to indicate the optimum scraping direction for removal of formation material by an associated cutting element. The optimum scraping direction may vary from one row of cutting elements to the next row of cutting elements on each cutter cone assembly. See
Various techniques may be used to determine optimum orientation of cutting elements and associated scraping for removal of material from a downhole formation using roller cone drill bits. U.S. Pat. No. 6,095,262 entitled “Roller-Cone Bits, Systems, Drilling Methods, And Design Methods With Optimization Of Tooth Orientation” discloses examples of some techniques for optimizations based in part on determining radial and tangential scraping motion of inserts or teeth during engagement of a roller cone bit with a downhole formation. For some applications equivalent tangent scraping distance and equivalent radial scraping distance along with calculations of ratios between drill bit rotation speed and cone rotation speed may be used to determine optimum orientation of cutting elements and associated scraping direction for removal of material from a downhole formation. Depending upon specific design characteristic of each cutting element such as size and configuration of an associated crest, the orientation of the crest of a cutting element for optimum penetration of a formation may be approximately perpendicular to the optimum orientation of the crest of the same cutting element for removal of material from the same formation.
Conventional roller cone drill bits have frequently been formed with cutting elements oriented at different angles relative to each other to minimize tracking of the cutting elements during rotation of the drill bit.
For embodiments represented by cone assembly 30d first row or gauge row 72 preferably includes at least one cutting element 60 with its associated crest 68 extending generally perpendicular with respect to optimum scraping direction 70. Crest 68 of an adjacent cutting element 60 may be oriented parallel with optimum scraping direction 70.
Accordingly, the crests 68 of the at least one cutting element and the adjacent cutting element 68 are oriented at approximately ninety degrees relative to one another. In some embodiments, the orientations of the at least one cutting element crest 68 on the adjacent cutting element crest 68 may vary such that the orientation of the crests 68 may vary by ninety (90) degrees, with a variation of up to ten (10) degrees. In other embodiments, the variation in orientation of alternating crests 68 may be up to twenty (20) or thirty (30) degrees from the ninety (90) degree variation in orientation between alternating crests 68 described above.
For some applications cutting elements 60 may be disposed in second row 74 and third row 76 with a similar alternating pattern defined by crest 68 of one cutting element 60 extending generally perpendicular with respect to optimum scraping direction 70 and crest 68 of an adjacent cutting element 60 extending generally parallel with respect to optimum scraping direction 70.
Benefits of the present invention include recognizing that the optimum scraping direction may vary from one row of cutting elements to the next row of cutting elements on the same cutter cone assembly and orientating cutting elements and respective crests to provide either enhanced penetration or crushing of a formation or scraping or shearing for optimum removal of formation materials. The present invention also includes forming cutting elements with optimum dimensions and configurations for enhanced drilling efficiency.
Technical benefits of the present invention include selecting the number of cutting elements disposed in the gauge row of three (3) cone assemblies to optimize removal of formation materials and the number of cutting elements disposed to enhance penetration of the formation by a roller cone drill bit. Embodiments represented by
For other types of formations cutting element 60e aligned generally perpendicular with the optimum scraping direction 70 may be larger than cutting elements 60d extending generally parallel with optimum scraping direction 70. Technical benefits of the present invention include varying the size of cutting elements to optimize formation penetration, removal of formation materials and downhole drilling life of the associated cutting elements based on factors such as overall formation hardness and any variations in formation hardness.
In
The present invention allows placing a greater concentration of hard materials which are often more expensive than other materials associated with forming a cutting element adjacent to the leading edge to provide enhanced resistance to abrasion and wear. For some applications there may be advantages to using relatively soft material to form the leading portion of a cutting element and harder material to form the trailing portion of the cutting element. This arrangement will be discussed with respect to cutting element 360f of
Technical benefits of the present invention include forming craters 82 and 84 in a wellbore to optimize fracturing and splitting of adjacent formation materials. Cutting elements may also be oriented to increase fracturing or splitting of any formation materials extending between or “bridging” adjacent craters 82 and 84. The size and configuration of the cutting elements may be varied to minimize the presence of bridging materials.
The distance between adjacent cutting elements 60 in each row may be reduced to minimize the presence of any bridging materials between resulting craters 82 and 84. The spacing between adjacent rows of cutting elements may be adjusted in accordance with teachings of the present invention to minimize the presence of any bridging materials between one ring of craters 82 and 84 and an adjacent ring of craters 82 and 84. Cutting elements may also be oriented in accordance with teachings of the present invention such that enhanced penetration of a formation results in increased fracturing and splitting of bridging materials to allow even more efficient formation removal.
Roller cone drill bit 320 as shown in
Cutting structures may be formed on each cone assembly 330a, 330b and 330c in accordance with teachings of the present invention. For example, cutting elements or teeth 360 may be formed in rows on each cone assembly 330a, 330b and 330c with orientations similar to previously described cutting elements 60. Cutting element 360 may be disposed with crests 368 oriented for optimum penetration of a formation or for optimum removal of formation material as previously described with respect to cutting elements 60. Cutting elements 360 are typically formed using milling techniques. The resulting cutting elements 360 may sometimes be referred to as “milled teeth”.
In some embodiments cutting elements 360 may be provided such that the length of crests 368 of alternating milled teeth 360 vary in size. In certain embodiments this includes varying the size of alternating cutting elements 360 such that a larger cutting element having a longer crest 368 may be provided for strength in penetrating hard formations, followed by a smaller cutting element having a shorter crest oriented to maximize formation volume removal.
In some embodiments, cutting elements 360 are formed from the same material as the cone and also include a hard facing applied thereto. Such hard facing may be applied to the entire cutting element 360, to only the leading edge of cutting element 360, or only to the trailing edge of cutting element 360.
Technical benefits of the present invention include orienting a cutting element for optimum removal of formation materials or for optimum penetration of a formation along with optimum wear of the cutting element. For some types of formation it may be preferable for the leading portion of a cutting element to be formed with relatively hard material as compared with the trailing edge of the cutting element. For other applications it may be preferable to have the leading portion of a cutting element formed from relatively soft material and the trailing portion formed from relatively hard material. This arrangement may result in self sharpening of an associated cutting element.
Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alternations can be made herein without departing from the spirit and scope of the invention as defined by the following claims.
Claims
1. A roller cone drill bit for forming a wellbore in a subterranean formation comprising:
- a bit body having at least one support arm extending therefrom;
- a respective cone assembly rotatably mounted on each support arm for engagement with the formation to form the wellbore;
- each cone assembly having a gauge row and at least one other row of cutting elements;
- each cutting element having a crest extending from the associated cone assembly for engagement with adjacent portions of the formation;
- each cone assembly and associated cutting elements having a scraping direction for optimum removal of formation materials;
- the crests of the cutting elements in the at least one other row arranged with the crest of a first cutting element oriented generally perpendicular relative to the scraping direction to optimize volume removal of formation material by the first cutting element;
- a second cutting element in the at least one other row disposed adjacent to the first cutting element;
- the crest of the second cutting element oriented generally perpendicular relative to the crest of the first cutting element to optimize penetration of the formation by the second cutting element; and
- the remaining cutting elements in the at least one other row arranged in an alternating pattern with the crest of one cutting element aligned for optimum volume removal of formation material and the crest of an adjacent cutting element aligned for optimum penetration of the formation.
2. The drill bit of claim 1 further comprising the first cutting element and the second cutting element cooperating with each other to form a series of generally T-shaped voids in the adjacent formation.
3. The drill bit of claim 1 further comprising the first cutting element and the second cutting element cooperating with each other to form a series of generally cross shaped voids in the adjacent formation.
4. The drill bit of claim 1 further comprising:
- a first row of the cutting elements cooperating with each other to form a series of overlapping, generally cross shaped voids in the adjacent formation;
- a second row of the cutting elements cooperating with each other to form a series of overlapping, generally cross shaped voids in the adjacent formation; and
- the cross shaped voids formed by the cutting elements of first row offset from the cross shaped voids formed by the cutting elements of the second row.
5. The drill bit of claim 1 further comprising at least one row of cutting elements cooperating with each other to form a series of overlapping T-shaped voids in the adjacent formation.
6. The drill bit of claim 1 further comprising at least one row of cutting elements cooperating with each other to form a series of generally cross-shaped voids in the adjacent formation.
7. A roller cone drill bit for forming a wellbore in a subterranean formation comprising:
- a bit body having at least one support arm extending therefrom;
- a respective cone assembly rotatably mounted on each support arm for engagement with the formation to form the wellbore;
- each cone assembly having at least one row of cutting elements;
- each cutting element having a crest extending from the associated cone assembly for engagement with adjacent portions of the formation;
- each cone assembly and associated cutting elements having a scraping direction for optimum removal of formation materials;
- the crests of the cutting elements in the at least one row arranged with the crest of a first cutting element oriented generally perpendicular relative to the scraping direction to optimize volume removal of formation material by the first cutting element;
- a second cutting element in the at least one row disposed adjacent to the first cutting element;
- the crest of the second cutting element oriented generally perpendicular relative to the crest of the first cutting element to optimize penetration of the formation by the second cutting element;
- the remaining cutting elements in the at least one row arranged in an alternating pattern with the crest of one cutting element aligned for optimum volume removal of formation material and the crest of an adjacent cutting element aligned for optimum penetration of the formation;
- at least one cone assembly having at least a gauge row of cutting elements, a second row of cutting elements and a third row of cutting elements spaced from each other;
- the respective crests of the cutting elements in the gauge row of cutting elements of the at least one cone assembly arranged in an alternating pattern defined in part by the crest of one of the cutting elements oriented generally perpendicular to the associated scraping direction and the crest of the adjacent cutting element oriented generally parallel to the associated scraping direction;
- the respective crests of the cutting elements in second row of cutting elements of the at least one cone assembly arranged in an alternating pattern defined in part by the crest of one of the cutting elements oriented generally perpendicular to the associated scraping direction and the crest of the adjacent cutting element oriented generally parallel to the associated scraping direction; and
- the respective crests of the cutting elements in the third row of cutting elements of the at least one cone assembly arranged in an alternating pattern defined in part by the crest of one of the cutting elements oriented generally perpendicular to the associated scraping direction and the crest of the adjacent cutting element oriented generally parallel to the associated scraping direction.
8. A roller cone drill bit for forming a wellbore in a subterranean formation comprising:
- a bit body having at least one support arm extending therefrom;
- a respective cone assembly rotatably mounted on each support arm for engagement with the formation to form the wellbore;
- each cone assembly having at least one row of cutting elements;
- each cutting element having a crest extending from the associated cone assembly for engagement with adjacent portions of the formation;
- each cone assembly and associated cutting elements having a scraping direction for optimum removal of formation materials;
- the crests of the cutting elements in the at least one row arranged with the crest of a first cutting element oriented generally perpendicular relative to the scraping direction to optimize volume removal of formation material by the first cutting element;
- a second cutting element in the at least one row disposed adjacent to the first cutting element;
- the crest of the second cutting element oriented generally perpendicular relative to the crest of the first cutting element to optimize penetration of the formation by the second cutting element;
- the remaining cutting elements in the at least one row arranged in an alternating pattern with the crest of one cutting element aligned for optimum volume removal of formation material and the crest of an adjacent cutting element aligned for optimum penetration of the formation;
- a first row of the cutting elements cooperating with each other to form a series of overlapping, generally T shaped voids in the adjacent formation;
- a second row of cutting elements cooperating with each other to form a series of overlapping, generally T shaped voids in the adjacent formation; and
- the T-shaped voids formed by the cutting elements of the first row offset from the T voids formed by the cutting elements of the second row.
9. The drill bit of claim 8 further comprising the cutting elements selected from the group consisting of inserts and milled teeth.
10. A roller cone drill bit operable to form a wellbore in a subterranean formation comprising:
- a bit body having at least one support arm extending therefrom;
- a respective cone assembly rotatably mounted on each support arm for engagement with the formation to form the wellbore;
- each cone assembly having at least a gauge row of cutting elements, a second row of cutting elements and a third row of cutting elements spaced from each other;
- each cutting element having a crest extending from the associated cone assembly for engagement with adjacent portions of the formation;
- the respective crests of the cutting elements in the gauge row of at least one cone assembly arranged generally perpendicular to an associated scraping direction;
- the respective crests of the cutting elements in the second row of cutting elements of the at least one cone assembly arranged generally parallel to the associated scraping direction; and
- the respective crests of the cutting elements in the third row of cutting elements oriented generally perpendicular to the associated scraping direction.
11. The drill bit of claim 10 further comprising:
- three support arms extending from the bit body;
- first, second and third cone assemblies rotatably mounted on respective support arms;
- the respective crest for each cutting element in the gauge row of the first cone assembly oriented generally perpendicular to the associated scraping direction;
- the respective crest for each cutting element in the gauge row of the second cone assembly oriented generally parallel to the associated scraping direction; and
- the respective crest of each cutting element in the gauge row of the third cone assembly arranged in an alternating pattern defined in part by the crest of one of the cutting elements oriented generally perpendicular to the associated scraping direction and the crest of the adjacent cutting element oriented generally parallel to the associated scraping direction.
12. A roller cone drill bit comprising:
- a bit body having at least one support arm extending therefrom;
- a respective cone assembly rotatably mounted on each support arm for engagement with a subterranean formation to form a wellbore;
- each cone assembly having at least a first row of cutting elements and a second row of cutting elements;
- each cutting element having a crest extending from the associated cone assembly for engagement with adjacent portions of the formation;
- each cone assembly and associated cutting elements having respective scraping directions for optimum removal of formation materials;
- the crests of the cutting elements in the first row oriented generally perpendicular relative to the optimum scraping direction for removal of formation materials by the cutting element of the first row; and
- the crests of the cutting elements in the second row oriented generally parallel relative to the optimum scraping direction for removal of formation materials by the cutting elements in the second row.
13. The drill bit of claim 12 further comprising the cutting elements in the second row formed from materials having increased hardness as compared with materials used to form the cutting elements in the first row.
14. The drill bit of claim 12 further comprising the length of the crests of the cutting element in the first row selected to be longer than the crests of the cutting elements in the second row.
15. A roller cone drill bit comprising:
- a bit body having at least three support arms extending therefrom;
- a respective cone assembly rotatably mounted on each support arm for engagement with a subterranean formation to form a wellbore;
- each cone assembly having a gauge row of cutting elements;
- each cutting element having a crest extending from the respective cone assembly for engagement with adjacent portions of the formation;
- each cone assembly and associated cutting elements having an optimum scraping direction for removal of formation materials;
- the crest of the cutting elements in the gauge row of the first cone assembly oriented generally perpendicular relative to the optimum scraping direction for removal of formation materials by the gauge row of the first cone assembly;
- the crests of the cutting elements in the gauge row of the second cone assembly oriented generally parallel relative to an optimum scraping direction to enhance penetration of the formation by the gauge row of the second cone assembly;
- the crests of the cutting elements of the gauge row of the third cone assembly arranged with the crest of a first cutting element oriented generally perpendicular relative to the optimum scraping direction for removal of the formation materials and the crest of a second cutting element in the gauge row of the third cone assembly disposed approximately perpendicular to the crest of the first cutting element to enhance penetration of the formation; and
- the remaining cutting elements in the gauge row of the third cone assembly arranged in an alternating pattern with the crest of one cutting element aligned for optimum removal of formation materials and the crest of an adjacent cutting element aligned for enhanced penetration of the formation.
16. The drill bit of claim 15 further comprising the cutting elements oriented generally perpendicular relative to the optimum scraping direction having dimensions larger than the cutting elements oriented generally parallel with the optimum scraping direction.
17. The drill bit of claim 15 further comprising the cutting elements oriented generally perpendicular relative to the optimum scraping direction having dimensions smaller than the cutting elements oriented generally parallel with the optimum scraping direction.
18. The drill bit of claim 15 further comprising the cutting elements oriented generally perpendicular relative to the optimum scraping direction formed from materials having increased hardness as compared with materials used to form the cutting elements oriented generally parallel with the optimum scraping direction.
19. The drill bit of claim 15 further comprising the cutting elements oriented generally parallel with the optimum scraping direction formed from materials having increased hardness as compared with materials used to form the cutting elements oriented generally perpendicular relative to the optimum scraping direction.
20. A method for forming a roller cone drill bit to drill a wellbore in a mixed formation of soft material and hard material comprising;
- forming a bit body with at least three support arms extending therefrom;
- rotatably mounting a cone assembly on each support arm;
- forming at least a first row of cutting elements and a second row of cutting elements on each cone assembly with a respective crest extending from each cutting element for engagement with adjacent portions of the mixed formation;
- orienting the crest of cutting elements in the first row generally perpendicular relative to an optimum scraping direction for removal of formation materials by the cutting elements of the first row;
- orienting the crest of cutting elements in the second row in a direction generally parallel with the optimum scraping direction to enhance penetration of the formation by the cutting element of the second row; and
- selecting the number of cutting elements with crests oriented for removal of formation materials and the number of cutting elements with crests oriented for penetration of the formation to optimize downhole drilling efficiency of the drill bit.
1209299 | December 1916 | Hughes |
1263802 | April 1918 | Reed |
1394769 | October 1921 | Sorensen |
1847981 | March 1932 | Reed |
2038386 | April 1936 | Scott et al. |
2117679 | May 1938 | Reed |
2122759 | July 1938 | Scott |
2132498 | October 1938 | Smith |
2165584 | July 1939 | Smith et al. |
2230569 | February 1941 | Howard et al. |
2496421 | February 1950 | Stokes |
2728559 | December 1955 | Boice et al. |
2851253 | September 1958 | Boice |
4056153 | November 1, 1977 | Miglierini |
4187922 | February 12, 1980 | Phelps |
4285409 | August 25, 1981 | Allen |
4334586 | June 15, 1982 | Schumacher |
4343371 | August 10, 1982 | Baker, III et al. |
4343372 | August 10, 1982 | Kinzer |
4393948 | July 19, 1983 | Fernandez |
4408671 | October 11, 1983 | Munson |
4427081 | January 24, 1984 | Crawford |
4455040 | June 19, 1984 | Shinn |
4611673 | September 16, 1986 | Childers et al. |
4627276 | December 9, 1986 | Burgess et al. |
4657093 | April 14, 1987 | Schumacher |
4738322 | April 19, 1988 | Hall et al. |
4776413 | October 11, 1988 | Forsberg |
4804051 | February 14, 1989 | Ho |
4815342 | March 28, 1989 | Brett et al. |
4848476 | July 18, 1989 | Deane et al. |
4889017 | December 26, 1989 | Fuller et al. |
5010789 | April 30, 1991 | Brett et al. |
5027913 | July 2, 1991 | Nquyen |
5042596 | August 27, 1991 | Brett et al. |
5131478 | July 21, 1992 | Brett et al. |
5131480 | July 21, 1992 | Lockstedt et al. |
5137097 | August 11, 1992 | Fernandez |
5197555 | March 30, 1993 | Estes |
5216917 | June 8, 1993 | Detournay |
5224560 | July 6, 1993 | Fernandez |
RE34435 | November 9, 1993 | Warren et al. |
5285409 | February 8, 1994 | Hwangbo et al. |
5291807 | March 8, 1994 | Vanderford |
5305836 | April 26, 1994 | Holbrook et al. |
5311958 | May 17, 1994 | Isbell et al. |
5318136 | June 7, 1994 | Rowsell et al. |
5341890 | August 30, 1994 | Cawthorne et al. |
5351770 | October 4, 1994 | Cawthorne et al. |
5370234 | December 6, 1994 | Sommer, Jr. et al. |
5372210 | December 13, 1994 | Harrell |
5394952 | March 7, 1995 | Johns et al. |
5415030 | May 16, 1995 | Jogi et al. |
5416697 | May 16, 1995 | Goodman |
5421423 | June 6, 1995 | Huffstutler |
5456141 | October 10, 1995 | Ho |
5513711 | May 7, 1996 | Williams |
5579856 | December 3, 1996 | Bird |
5595252 | January 21, 1997 | O'Hanlon |
5595255 | January 21, 1997 | Huffstutler |
5605198 | February 25, 1997 | Tibbitts et al. |
5636700 | June 10, 1997 | Shamburger, Jr. |
5697994 | December 16, 1997 | Packer et al. |
5704436 | January 6, 1998 | Smith et al. |
5715899 | February 10, 1998 | Liang et al. |
5730234 | March 24, 1998 | Putot |
5767399 | June 16, 1998 | Smith et al. |
5794720 | August 18, 1998 | Smith et al. |
5812068 | September 22, 1998 | Wisler et al. |
5813480 | September 29, 1998 | Zaleski, Jr. et al. |
5813485 | September 29, 1998 | Portwood |
5839526 | November 24, 1998 | Cisneros et al. |
5853245 | December 29, 1998 | Price |
5967245 | October 19, 1999 | Garcia et al. |
6002985 | December 14, 1999 | Stephenson |
6003623 | December 21, 1999 | Miess |
6012015 | January 4, 2000 | Tubel |
6021377 | February 1, 2000 | Dubinsky et al. |
6029759 | February 29, 2000 | Sue et al. |
6044325 | March 28, 2000 | Chakravarthy et al. |
6057784 | May 2, 2000 | Schaaf et al. |
6095262 | August 1, 2000 | Chen |
6095264 | August 1, 2000 | Dillard |
6109368 | August 29, 2000 | Goldman et al. |
6119797 | September 19, 2000 | Hong et al. |
6142247 | November 7, 2000 | Pessier |
6176329 | January 23, 2001 | Portwood et al. |
6213225 | April 10, 2001 | Chen |
6241034 | June 5, 2001 | Steinke et al. |
6260635 | July 17, 2001 | Crawford |
6269892 | August 7, 2001 | Boulton et al. |
6308790 | October 30, 2001 | Mensa-Wilmot et al. |
6348110 | February 19, 2002 | Evans |
6349595 | February 26, 2002 | Civolani et al. |
6374930 | April 23, 2002 | Singh et al. |
6401839 | June 11, 2002 | Chen |
6412577 | July 2, 2002 | Chen |
6499547 | December 31, 2002 | Scott et al. |
6516293 | February 4, 2003 | Huang et al. |
6527068 | March 4, 2003 | Singh et al. |
6533051 | March 18, 2003 | Singh et al. |
6581699 | June 24, 2003 | Chen et al. |
6607047 | August 19, 2003 | Swadi et al. |
6619411 | September 16, 2003 | Singh et al. |
6729420 | May 4, 2004 | Mensa-Wilmot |
6848518 | February 1, 2005 | Chen et al. |
6856949 | February 15, 2005 | Singh et al. |
6879947 | April 12, 2005 | Glass |
7020597 | March 28, 2006 | Oliver et al. |
7079996 | July 18, 2006 | Stewart et al. |
7147066 | December 12, 2006 | Chen et al. |
20010042642 | November 22, 2001 | King |
20040045742 | March 11, 2004 | Chen |
20040104053 | June 3, 2004 | Chen |
20040118609 | June 24, 2004 | Dennis |
20040167762 | August 26, 2004 | Chen |
20040254664 | December 16, 2004 | Centala et al. |
20050015230 | January 20, 2005 | Centala et al. |
20060032674 | February 16, 2006 | Chen et al. |
20060074616 | April 6, 2006 | Chen |
2082755 | August 1991 | CN |
0384734 | August 1990 | EP |
0511547 | April 1992 | EP |
0511547 | April 1992 | EP |
0511547 | April 1992 | EP |
1006256 | June 2000 | EP |
2186715 | August 1987 | GB |
2241266 | August 1991 | GB |
2 300 208 | October 1996 | GB |
2305195 | April 1997 | GB |
2327962 | February 1999 | GB |
2363409 | June 2001 | GB |
2365899 | February 2002 | GB |
2367578 | April 2002 | GB |
2367579 | April 2002 | GB |
2367626 | April 2002 | GB |
2384567 | July 2003 | GB |
2388857 | November 2003 | GB |
2400696 | October 2004 | GB |
1654515 | March 1988 | SU |
1691497 | May 1988 | SU |
1441051 | November 1988 | SU |
1768745 | October 1992 | SU |
- Patent Acts 1977: Error in Search Report, Application No. GB0516638.4, 2 pgs, May 24, 2006.
- Decision revoking European Patent No. EP-B-1117894, 16 pgs, May 15, 2006.
- Notification of European Search Report for Patent application No. 04025232.5-2315, pages, Apr. 4, 2006.
- Notification of European Search Report for Patent application No. 04025234.8-2315, 3 pages, Arp. 4, 2006.
- Notification of European Search Report for Patent application No. 04025233.0-2315, 3 pages, Apr. 11, 2006.
- Maurer, W.C., “The Perfect-Cleaning Theory of Rotary Drilling”, Journal of Petroleum Technology, SPE, pp. 1207-1274, Nov. 1962.
- Ma. D., et al. “A New Method for Designing Rock Bit”, SPE Proceedings, vol. 22431, XP008058830, 10 pages, Mar. 24, 1992.
- Notification of Great Britain Search Report for Application No. GB 0516638.4 (4 pages), Jan. 5, 2006.
- Notification of Great Britain Search Report for Application No. GB 0523735.9 (3 pages), Jan. 31, 2006.
- Communication from European Patent Office regarding opposition; Application No. 99945376.4—1266/1117894 through the Munich office (5 pages), Feb. 15, 2006.
- Notification of European Search Report for Patent Application No. EP 04025560.6-2315 (4 pages), Feb. 24, 2006.
- Notification of Eurpean Search Report for Patent Application No. EP 04025561.4-2315 (4 pages), Feb. 24, 2006.
- Approved Judgment before Ho. Pumfrey, High Court of Justice, Chancery Division, Patents Court, Case HC04C00114, 00689, 00690, (Halliburton v. Smith Internal.), Royal Courts of Justice, Strand, London. (84 pages), Feb. 24, 2006.
- Notification of European Search Report for Patent Appliation No. EP 04025562.2-2315 (4 pages), Feb. 24, 2006.
- Notification of European Search Report for Patent Application No. EP 04025232.2-2315 (4 pages), Feb. 24, 2006.
- Approved Judgement, Case No: HC 04 C 00114 00689 00690, Royal Courts of Justice, BEtween: Halliburton Energy Services, Inc. and (1) Smith International (North Sea) Limited (2) Smith International, Inc. (3) Smith International Italia SpA.
- W.C. Maurer, “The “Perfect-Cleaning”Theory of Rotary Drilling,” Journal of Petroleum Technology, pp. 1175, 1270-1274.
- MA Dekun, The Operational Mechanics of the Rock Bit, Petroleum Industry Press, Beijing, China, 1996.
- D. Ma, D. Zhou & R. Deng, The Computer Stimulation of the Interaction Between Roller Bit and Rock, (1995).
- Shilin Chen, Linear and Nonlinear Dynamics of Drillstrings, 1994-1995.
- D. Ma, & J.J. Azar, Dynamics of Roller Cone Bits, Dec. 1985.
- D.K.Ma & S.L. Yang, Kinamatics of the Cone Bit, Jun. 1985.
- Dma & J.J. Azar, A New Way to Characterize the Gouging-Scraping Action of Roller Cone Bits, 1989.
- Russian bit catalog listing items “III 190, 5 T-UB-1” and “III 109,5 TKZ-UB”, prior 1997.
- L.E. Hibbs, Jr., et al, Diamond Compact Cutter Studies for Geothermal Bit Design, Nov. 1978.
- M.C. Sheppard, et al., “Forces at the Teeth of a Drilling Rollercone Bit: Theory and Experiment”, Proceedings: 1988 SPE Annual Technical Conference and Exhibition; Huston, TX, USA, Oct. 2-5, 1988, vol. Delta, 1988, pp. 253-260 18042, XP002266080, Soc. Pet Eng AIME Pap SPE 1988 Publ by Soc of Petroleum Engineers of AIME, Richardson, TX, USA.
- Adam T. Bourgoyne Jr et al., “Applied Drilling Engineering”, Society of Petroleum Engineers Textbook Series, 1991.
- Plaintiff's Original Complaint for Patent Infringement and Jury Demand, filed Sep. 6, 2002 in the United States District Court for the Eastern District of Texas, Sherman Division, Civil Action No. 4-02CV269, Halliburton Energy Services, Inc. v. Smith International, Inc., 4 pages.
- Answer and Counterclaim of Smith International, filed Mar. 14, 2003, in the United States District Court for the Eastern District of Texas, Sherman Division, Civil Action No. 4-02CV269, Halliburton Energy Servies, Inc. v. Smith International, Inc., 6 pages.
- Response of Plaintiff and Counterclaim Defendant to Defendant's Counterclaim of Declaratory Judgment, filed Apr. 3, 2003, in the United States District Court for the Eastern District of Texas, Sherman Division, Civil Action No. 4-02CV269, Halliburton Energy Services, Inc. v. Smith International, Inc., 3 pages.
- First Amended Answer and Counterclaim of Smith International, filed Oct. 9, 2003, in the United States District Court for the Eastern District of Texas, Sherman Division, Civil Action No. 4-02CV269, Halliburton Energy Services, Inc. v. Smith International, Inc., 8 pages.
- J.P. Nguyen, “Oil and Gas Field Development Techniques: Drilling”(translation 1996, from French original 1993).
- T.M. Warren et al, “Drag-Bit Performance Modeling”, SPE Drill Eng. Jun. 1989, vol. 4, No. 2, pp. 119-127 15618, XP002266079.
- “Making Hole”, part of Rotary Drilling Series, edited by Charles Kirkley, 1983.
- T.M. Warren, “Factors Affecting Torque for A Roller Cone Bit”, JPT J PET Technol Sep. 1984, vol. 36, No. 10, pp. 1500-1508, XP002266078.
- “Drilling Mud”, part of Rotary Drilling Series, edited by Charles Kirkley, 1984.
- H.G. Benson, “Rock Bit Design, Selection and Evaluation”, presented at the spring meeting of the pacific coast district, American Petroleum Institute, Division of Producation, Los Angeles, May 1956.
- Memorandum Opinion of Judge Davis, signed Feb. 13, 2004, in the United States District Court for the Eastern District of Texas, Sherman Division, Civil Action No. 4-02CV269, Halliburton Energy Services, Inc. v. Smith International, Inc., 37 pages (including fax coversheet).
- Final Judgment of Judge Davis, signed Aug. 13, 2004, in the United States District Court for the Eastern District of Texas, Sherman Division, Civil Action No. 4002CV269, Halliburton Energy Services, Inc. v. Smith International, Inc., 3 pages.
- Sworn written statement of Stephen Steinke and Exhibits SS-1 to SS-6, Oct. 13, 2004.
- J.C. Estes, “Selecting the Proper Rotary Rock Bit”, Journal of Petroleum Technology, pp. 1359-1367, Nov. 1971.
- D.K. Ma, A New Method of Description of Scraping Characteristics of Roller Cone Bit, Petroleum Machinery, Jul. 1988 (English translations with original Chinese version attached).
- Wilson C. Chin, Wave Propagation in Petroleum Engineering, 1994.
- Sikarskie, et. al., “Penetration Problems in Rock Mechanics”, American Society of Mechanical Engineers, Rock Mechanics Symposium, 1973.
- Dykstra, et. al., “Experimental Evaluations of Drill String Dynamics”, Amoco Report No. SPE 28323, 1994.
- Kenner and Isbell, “Dynamic Analysis Reveals Stability of Roller Cone Rock Bits”, SPE 28314, 1994.
- Brochure entitled “Twist & Shout”, (SB2255.1001), 4 pages.
- Drawing No. A46079 Rock Bit and Hole Opener; Security Engineering Co., Inc., Whittier, California, Sep. 14, 1946.
- “Machino Export”, Russia, 4 pages, 1974.
- R.K. Dropek, “A Study to Determine Roller Cone Cutter Offset Effects at Various Drilling Depths” American Society of Mechanical Engineers. 10 pages, Aug. 1, 1979.
- U.S. Appl. No. 10/325,650, filed Dec. 19, 2002 by John G. Dennis, entitled Drilling with Mixed Tooth Types.
- British Search Report for GB Patent Application No. 0504304.7, 4 pgs, Apr. 22, 2005.
- British Search Report for GB Patent Application No. 0503934.2, 3 pgs, May 16, 2005.
- B.L. Steklyanov, et al, “Improving the Effectiveness of Drilling Tools,” Series KhM-3, Oil Industry Machine Building, pub. Central Institute for Scientific and Technical Information and Technical and Economic Research on Chemical and Petroleum Machine Building, Tsintikhimneftemash, Moscow translated from Russian), 1991.
- Energy Balanced Series Roller Cone Bits, www.halliburton.com/oil—gas/sd1380.jsp.
- Ashmore, et al., Stratapax™ Computer Program, Sandia Laboratories, Albuquerque, NM, (76 pages).
- F.A.S.T.™ Technology Brochure entitled “Tech Bits”, Security/Dresser Industries (1 page), Sep. 17, 1993.
- Sii PLUS Brochure entitled “The PDC Plus Advantage”, from Smith International (2 pages).
- Specification sheet entitled “SQAIR Quality Sub-Specification”, Shell Internationale Petroleum Mij. B. V., The Hauge, The Netherlands, 1991 (2 Pages).
- Brochure entitled “FM2000 Series-Tomorrow's Technologies for Today's Drilling.”, Security DBS, Dresser Industries, Inc., 1994 ( Pages).
- Brochure entitled “FS2000 Series-New Steel Body Technology Advances PDS Bit Performance and Efficiency”, Security DBS, Dresser Industries, Inc. (6 pages), 1997.
- Communication of a Notice of Opposition filed Oct. 14, 2004, with the European Patent Office.
- Brief Communication from European Patent Office enclosing letter from the opponent of Oct. 13, 2004.
- Composite Catalog of Oil Filed Equipment & Services, 27th Revision 1666-67 vol. 3, 1966.
- Lecture Handouts, Rock Bit Design, Dull grading, Selection and Applications, presented by Reed Rock bit Company, Oct. 16, 1980.
- Longer Useful Lives for Roller Bits Cuts Sharply into Drilling Costs, South African Mining & Engineering Journal, vol. 90, pp. 39-43, Mar. 1979.
- Rabia, H., Oilwell Drilling Engineering: Principles and Practice, University of Newcastle upon Tyne, 331 pages, 1985.
- Brief Communication from European Patent Office enclosing letter from the opponent dated Dec. 2, 2004 (074263.0281).
- Halliburton Revolutionizes PDC Drill Bit Design with the Release of FM3000, 2003 Press Release, 2 pgs, Aug. 8, 2005.
- D Stroud et al., “Development of the Industry's First Slimhole Point-the-Bit Rotary Steerable System,” Society of Petroleum Engineers Inc, 4 pgs, 2003.
- J.A. Norris, et al., “Development and Successful Application of Unique Steerable PDC Bits,” Copyright 1998 IADC/SPE Drilling Conference, 14 pgs, Mar. 3, 1998.
- Halliburton Revolutionizes PDC Drill Bit Design with the Release of FM3000, 2003 Press Releases, 2 pgs, May 5, 2003.
- O. Vincke, et al., “Interactive Drilling: The Up-To-Date Drilling Technology,” Oil & Gas Science and Technology Rev. IFP, vol. 59, No. 4, pp. 343-356, Jul. 1004.
- Halliburton catalogue item entitled: EZ-Pilot (TM) Rotary Steerable System (1 page), Jul. 24, 2006.
- Halliburton catalogue item entitled: Geo-Pilot (R) Rotary Steerable System 1 page), Jul. 24, 2006.
- Halliburton catalogue item entitled: SlickBore (R) Matched Drilling System (1 page), Jul. 24, 2006.
- International Search Report, PCT/US2006/030830, 11 pages, Dec. 19, 2006.
- Menand et al., Classification of PDC Bits According to their Steerability, SPE, 11 pgs, 2003.
- International Search Report, PCT/US2006/030803, 11 pgs, Dec. 19, 2006.
- Hare et al., Design Index: A Systematic Method of PDC Drill-Bit Selection, SPE, 15 pgs, 2000.
- Sutherland et al. “Development & Application of Versatile and Economical 3D Rotary Steering Technology” AADE, Emerging Technologies (pp. 2-16), 2001.
Type: Grant
Filed: Feb 9, 2005
Date of Patent: Feb 26, 2008
Patent Publication Number: 20050133273
Assignee: Halliburton Energy Services, Inc. (Carrollton, TX)
Inventors: Shilin Chen (The Woodlands, TX), James S. Dahlem (Midlothian, TX)
Primary Examiner: Hoang Dang
Attorney: Baker Botts L.L.P.
Application Number: 11/054,395
International Classification: E21B 10/16 (20060101);